Classification, distribution and genesis of

Southern African iron ore resources Nicolas J Beukes

PPM and CIMERA, Department of Geology

University of Johannesburg, Aucklandpark 2006

South Africa

nbeukes@uj.ac.za

PPM

• Broad classification of iron ores

1) Magmatic,

2) Oolitic,

3)BIF-hosted

1) Metamorphic Bif or taconite ores

2) Supergene

3) Hydrothermal

4) Supergene-modified hydrothermal

4) Detrital

5) Black band

10

10-

10. Taconite Damara orogen

Palaborwa Magnetite

Carbonatite surrounded by phoscorite

Carbonatite 15-30 wt % magnetite with < 1 wt %

TiO2

Phoscorite 50 wt % magnetite at up to 5 wt %

TiO2

Produced about 5 million tons of magnetite per

annum since early 1960’s

Timeball Hill Oolitic Iron Ore

Age 2.32 Ga

Resource

6000 Mt at 40 - 55 wt % Fe

Oolitic ironstone

270 290

310

240

260

0

50

100

150

0

50

100

150

200

30

0

P

Delta lobe FerricreteOolitic ironstone

AbundantCommonScarce

Major paleocurrent direction

Quartzite thickness contours50m

0 100km

NP- Pretoria

A

Quartzite isolith map of the Timeball Hill Formation indicating the distribution of oolitic ironstone. Modified from Button, 1973.

Oolitic Ironstone, Pretoria Group, 2,32 Ga

1mm

Backscatter SEM image of a pisolite in pisolitic mudclast conglomerate

Taconitic Iron Ores

Simply metamorphosed BIF with coarser recrystallization

of magnetite.

Low grade 30-45 wt % Fe

Milling and magnetic or heavy media separation

Taconite Ore

• Metamorphosed Bifs

• Limpopo Belt

• Namaqua-Natal Belt

• Damara Belt

Shakawe

Congo-Angola Craton

Kalahari Craton

Kaapvaal Craton

Zimbabwe

Craton

Dordabis

Prospect

area

Shakawe

Correlative to:

Chuos and

Grand

Conglomerate

~745 my

A

B

Fe = ~35-40 wt %

A B

Strat top

Shakawe: De Witt, 2013

Dordabis

Malyi Khingan

Urucum

Otjosondu

Rapitan

Sturtian Glaciation: ~745 my

Shakawe

Congo-Angola Craton

Kalahari Craton

Kaapvaal Craton

Zimbabwe

Craton

Dordabis

Bushmanland succession: ~1450 - 1280 Ma

Mn-IF

Overturned Limb

and Cores

Fe-ore

Origin of high grade BIF-hosted iron ore

deposits

Primary Sedimentary

Host Rock (BIF)

Supergene Enrichment

Superlarge deposits

(2 - 17 Billion tons)

Hydrothermal enrichment

Mineable very large deposits

(0,3-1 Billion tons)

From African Iron Ltd, ASX Announcement, 27 Jan. 2011.

Ancient supergene ore deposit : Sishen-type, South Africa

Karst-hosted Age ~ 2,0 Ga

Resource: 2 -2,5 billion tons

Grade: Laminated hard lumpy ore 65 wt % Fe

Conglomeratic ore ~ 63 wt % Fe

Griqualand West

geological map

Sishen-type deposit, Maremane dome

Hematized iron formation

Large resources for upgrading

High-grade hematite

BIFOre

Dolomite

Manganese marker

0 2 km

Source: Kumba

Beeshoek/Olynfontein Plan view

Beeshoek

Olynfontein

Sishen-type Conglomeratic Ore

Genetic model for Sishen-type ores

Sishen-type ore body: Exposed ancient sinkhole structure

Inverted topgraphy

Griqualand West

geological map

Extension of unconformity-bounded

Gamagara/Mapedi Fe ores:

Age = Post Bushveld-Pre Hartley

2050-1925 Ma = Waterberg UBS II

Hotazel Rooinekke

Thabazimbi deposit, South Africa

Thabazimbi ore

Carbonate

ore

Thabazimbi fluid inclusions

Mt Tom Price

Simandou in West Africa

Aguas Claras deposit, Brazil

Ngwenya

Differentiation between supergene and hydrothermal BIF-hosted

Fe ore

REE and Oxygen isotopic composition

Conclusion

Southern Africa has some potential for finding additional resources of

high-grade ancient supergene Sishen-type iron ore along the Pre-

Gamagara unconformity

Southern Africa has large potential for upgrading lower grade ore

resources both along the Pre-Gamagara unconformity and for taconitic

magnetite-rich ores in metamorphic belts.

Southern Africa has some potential for finding additional resources of

high-grade BIF-hosted hydrothermal iron ore deposits in Thabazimbi

and Prieska areas and in greenstone belts

Significant potential for magmatic Bushveld-type Ti-V magnetite ores

CIMERA Structure Host: PPM Research Centre, Geology Department, University of Johannesburg

Co-host: Economic Geology Research Institute (EGRI), School of Earth Sciences, University of the Witwatersrand.

Collaborating Partners: Rhodes University, Stellenbosch University, University of Fort Hare, University of Pretoria and University of Venda.

Director: Prof Nic Beukes, UJ, nbeukes@uj.ac.za

Co-director: Prof Judith Kinnaird, Wits, Judith.Kinnaird@wits.ac.za

CIMERA Focus The main focus is to train skilled

economic geologists through

undertaking postgraduate research

studies on mineral and energy

resources with focus on Africa but

not restricted to it.

Research Organization EIGHT FOCUS AREAS [5 – 8]

Critical Metals of the Future

• Rare Earth Elements, Tellurium, Molybdenum, Cobalt, Thallium, Lithium, Tungsten

New Bulk Mineral Resource Developments in Africa

• Iron, manganese and aluminum ores

Environmental and Medical Geology

• Solving and preventing acid mine drainage

• Carbon dioxide capture and storage

Public Awareness and Education

• Concentrate on steps required to create deeper public understanding for the need of an effective mineral resource industry in South Africa and Africa as a whole

Thank you for your attention Thank you for your attention

Beeshoek Iron Ore Mine